An advertisement by Company A says that three of every four doctors recommend pain reliever A over all other brands combined.
a. If the company based this claim on interviewing a random sample of doctors, explain how they could use a significance test to back up the claim.
b. Explain why this claim would be more impressive if it is based on a (i) random sample of 40 doctors than if it is based on a random sample of 4 doctors and (ii) random sample of 40 doctors nationwide than the sample of all 40 doctors who work in a particular hospital.